Optical tracking system for refueling

ABSTRACT

An aerial refueling system including a refueling drogue assembly including a refueling drogue and a refueling hose in captive relation with the refueling drogue and a drogue positioning system. The drogue positioning system including a radiation emitter, a radiation receiver and a signal processor. Then the radiation emitter is adapted to direct radiation to a positioning area a defined distance from the radiation emitter, the radiation carrying a modulated location signal containing information corresponding to positions within the positioning area. The radiation receiver is adapted to receive at least a portion of the emitted radiation carrying the modulated signal and output a signal to the signal processor indicative of the modulation of the location signal of the received radiation. And the signal processor is adapted to process the outputted signal and identify a position within the positioning area indicative of the location in the positioning area of the received radiation.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application claims priority to U.S. Provisional PatentApplication Ser. No. 60/656,084, entitled Optical Tracking System forRefueling, filed on Feb. 25, 2005, the contents of which areincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

Aerial refueling via the probe and drogue method is known. In anexemplary refueling scenario, a refueling drogue connected to arefueling hose is unreeled from a refueling aircraft (e.g., tankeraircraft) towards a receiver aircraft (an aircraft to be refueled), suchas a fighter plane, a helicopter, etc. The receiver aircraft has arefueling probe extending from the aircraft. The receiver aircraftmaneuvers to the refueling drogue and inserts its refueling probe intothe refueling drogue, at which point the refueling drogue “locks” ontothe refueling probe, and a transfer of fuel from the refueling aircraftto the receiver aircraft is conducted.

It is desirable that the drogue and the portion of the hose adjacent tothe drogue remain as stationary as possible, at least relative to therefueling aircraft, when extended from the refueling aircraft, at leastbefore contact between the drogue and the probe. Unfortunately, thehose-drogue combination has a relatively large dynamic response todisturbances, so when the drogue is subjected to wind gusts and/orturbulence, the hose-drogue combination moves relative to the refuelingaircraft, as forces imparted onto the drogue by the air cause the drogueto move. Moreover, the aircraft to be refueled also creates what iscalled a bow wave in-front of the aircraft to be refueled, which impartsforces onto the drogue, causing the drogue to move. These phenomenonmake it difficult to position the refueling probe of the aircraft to berefueled in the refueling drogue.

Thus, there is a need for a system that will substantially maintain theposition of a drogue, relative to a refueling aircraft, that has beenextended on a refueling hose so that the movement of the drogueresulting from wind/turbulence/bow wave, etc., is substantially reducedto improve the ease by which the refueling probe may be inserted in therefueling drogue.

SUMMARY OF THE INVENTION

An aerial refueling system comprising, a refueling drogue assemblyincluding a refueling drogue and a refueling hose in captive relationwith the refueling drogue and a drogue positioning system, the droguepositioning system including a radiation emitter, a radiation receiverand a signal processor, wherein the radiation emitter is adapted todirect radiation to a positioning area a defined distance from theradiation emitter, the radiation carrying a modulated location signalcontaining information corresponding to positions within the positioningarea, wherein the radiation receiver is adapted to receive at least aportion of the emitted radiation carrying the modulated signal andoutput a signal to the signal processor indicative of the modulation ofthe location signal of the received radiation, and wherein the signalprocessor is adapted to process the outputted signal and identify aposition within the positioning area indicative of the location in thepositioning area of the received radiation.

In another embodiment of the invention, the radiation emitter is adaptedto emit a focused optical beam and scan the focused optical beam overthe positioning area.

In yet another embodiment of the invention, the emitted radiation is afocused optical beam, wherein the modulated location signal includes aplurality of digital data blocks, the plurality of digital data blockscontaining information respectively corresponding to a plurality ofdiscrete positions within the positioning area that respectivelycorrespond to a current location of the focused beam within thepositioning area.

In another embodiment of the invention, the radiation emitter is adaptedto emit a focused optical beam and scan the focused optical beam overthe positioning area.

In another embodiment of the invention, there is an aerial refuelingsystem comprising a refueling drogue assembly including a refuelingdrogue and a refueling hose in captive relation with the refuelingdrogue, and a drogue positioning system, the drogue positioning systemincluding a radiation emitter, a radiation receiver, and a signalprocessor, wherein the radiation emitter is adapted to direct a beam ofemitted radiation to an area away from the radiation emitter, theradiation including discernable properties that vary in a correspondingmanner with varying orientation of the beam of radiation with respect tothe radiation emitter, wherein the radiation receiver is adapted toreceive at least a portion of the emitted radiation and output a signalto the signal processor indicative of one or more of the discernableproperties of the received radiation; and wherein the processor isadapted to process the outputted signal and identify a first virtualorientation indicative of an orientation of the receiver relative to theradiation emitter when at least a portion of the radiation was receivedby the receiver.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an aerial refueling operation according to thepresent invention.

FIG. 2 is a front view of an aerial refueling operation according to thepresent invention.

FIG. 3 is a side view of a drogue assembly according to the presentinvention.

FIG. 4 is a side view of a scanning operation according to the presentinvention.

FIG. 5 is a top view of a scanning operation according to the presentinvention.

FIG. 6 is a view of a focused optical elongated beam emitted by theradiation emitter.

FIG. 7 is a view of a focused optical elongated beam emitted by theradiation emitter impinging on a flat surface.

FIG. 8 is a view of a focused optical elongated beam emitted by theradiation emitter over an elapsed time.

FIG. 9 is a view of a focused optical elongated beam emitted by theradiation emitter impinging on a flat surface over an elapsed time.

FIG. 10 is a view of a focused optical elongated beam emitted by theradiation emitter.

FIG. 11 is a view of a focused optical elongated beam emitted by theradiation emitter impinging on a flat surface.

FIG. 12 is a view of a focused optical elongated beam emitted by theradiation emitter over an elapsed time.

FIG. 13 is a view of a focused optical elongated beam emitted by theradiation emitter impinging on a flat surface over an elapsed time.

FIG. 14 is a view of a virtual grid.

FIG. 15 is a view of a virtual grid superimposed over a scanning area.

FIGS. 16-17 present a schematic representing a two-pass scan over thevirtual grid.

FIG. 18 depicts a location of the virtual grid with respect to theradiation emitter.

FIGS. 19-20 present a schematic representing a two-pass scan over thevirtual grid, with the receiver positioned within the grid.

FIG. 21 presents a schematic of another type of scan utilized in thepresent invention.

FIG. 22 presents a symbolic representation of a digital data setutilized in an embodiment of the present invention.

FIG. 23 presents a schematic representing row orientation with respectto receiver aperture for a small beam/large aperture configuration.

FIGS. 24 and 25 schematically represent drogue positioning without theuse of a virtual grid.

FIGS. 26 to 31 schematically represent various galvo designs.

FIGS. 32 to 33 b schematically represent beam emission in elapsed time.

FIGS. 34-40 schematically represent an emitter according to anembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed towards systems, methods andapparatuses for enabling a drogue in general and a refueling drogue inparticular to determine its position relative to a fixed referencedpoint on the aircraft to which the drogue is coupled (e.g., refuelingaircraft). Moreover, the present invention is directed towards systems,methods and apparatuses for enabling a drogue in general and a refuelingdrogue in particular to substantially maintain a position relative tothe fixed reference point (also known as station keeping) based on thisdetermined position. In exemplary embodiment, this fixed reference pointis a radiation emitter on the wing of the refueling aircraft, as will bediscussed below. An exemplary embodiment of the present invention,coupled with exemplary scenarios utilizing the present invention, willnow be described followed by detailed discussions of particularembodiments of the present invention.

In a first embodiment of the present invention, as may be seen in FIGS.1-3, there is a refueling drogue assembly 100 comprising a refuelingdrogue 105 connected to a distal portion of a refueling hose 110 (withrespect to the attachment of the hose 110 to the aircraft 1000) that isin turn connected to an aircraft 1000. The aircraft 1000 includes aradiation emitter 200 that emits an optical beam in the generaldirection of the drogue assembly 105 (in particular, towards thereceiver 300 on the drogue assembly 105, as will be discussed below).The beam is emitted in a scanning fashion such that the beam scans anarea in relation to the radiation emitter in which the drogue 105(receiver 300) is likely located, based on, for example, empiricaldata/analytical data for a given air speed, altitude, etc. This area isindicated by reference number 400 in FIGS. 1-3. The optical bean emittedby the radiation emitter 200 scans this area in a manner such that adiscernable property of the optical beam changes as the orientation ofthe beam, with respect to the radiation emitter 200, changes. Thediscernable property of the optical beam that varies, in a controlledmanner, with changing orientation of the beam with respect to theradiation emitter may be, for example, different discrete digital datablocks carried on the beam by way of beam modulation.

Accordingly, in an exemplary scenario utilizing the present invention,the optical beam scans over the scanning area 400 in a manner such thata discernable property of the optical beam changes as the beam isscanning over the scanning area. That is, the discernable property isdifferent when the beam is located at one portion of the scanning area,as opposed to another portion of the scanning area, owing to the changein orientation of the beam with respect to the radiation emitter and thescanning area. This discernable property is carried on the optical beamand changes in a predetermined manner such that an analysis of thisdiscernable property will enable the location of the beam, relative tothe scanning area, to be determined. In this scenario, the radiationreceiver 300 on the drogue assembly 100 is configured to output a signalto a signal processor 500 (after receiving/sensing the optical beam asit passes over the receiver) onboard the drogue assembly 100. Thisoutputted signal from the receiver 300 is indicative of the discernableproperty carried on the optical beam that is received by the receiver.The signal processor 500 contains software and/or sufficient look uptables stored in a memory such that the signal processor 500, once itreceives the signal from the receiver 300, may analyze the receivedsignal and determine that the discernable property is indicative of aspecific beam orientation with respect to the radiation emitter 200 andthe scanning area 400. Because the geometry of the scanning area 400relative to the radiation emitter is known, the location of the receiver300 within the scanning area 400 may thus be determined by comparing thediscernable property of the received radiation to information stored ina look-up table. Because the geometry of the refueling drogue assembly100 relative to the receiver 300 is known, the position of the drogueassembly 100 relative to the radiation emitter may be determined.

As may be seen from FIGS. 1-3, the scanning area 400 is a square area inspace that passes through the receiver 300 on the refueling drogueassembly 100. This area 400 is approximately normal to the direction oftravel of the focused beam away from the radiation emitter (this isdiscussed in greater detail below).

Scanning

The operational characteristics of the radiation emitter 200 shall nowbe described. FIG. 4 depicts a side view of an exemplary embodiment ofthe radiation emitter 200 and receiver 300 arrangement. FIG. 4 is takenfrom the perspective view depicted in FIG. 1. FIG. 4 shows thatradiation emitter 200 emits a focused optical beam and moves that beamwithin lines 210 and 220. That is, from the side view of FIG. 4,radiation emitter 200 emits a beam in a scanning fashion such that thebeam moves within the area bounded by lines 210 and 220 so that thescanning area 400 may be scanned. By way of example only and not by wayof limitation, the radiation emitter 200 may emit a beam 202 at theorientation depicted in FIG. 4 at a time T₁, and then at a later timeT₂, emit a beam 204 at a different orientation from that of beam 202. Itis noted that in FIG. 4, the beam 202 is not intercepted by the receiver300, whereas the beam 204 is intercepted by the receiver 300. FIG. 5shows a top view of the radiation emitter 200 and the receiver 300depicted in FIG. 4. From FIG. 5, it can be seen that the radiationemitter 200 emits beams within the area bounded by line 230 and line240. Recognizing that FIG. 4 is a side view of the system and FIG. 5 isa top view of the system, a comparison of FIG. 4 with FIG. 5 shows thatthe volume (herein referred to as a scan zone and/or beam zone) boundedby lines 210 and 220 in FIG. 4 and lines 230 and 240 in FIG. 5 is in theshape of a cone, having its “top” located at the receiver 200. In theembodiment depicted in the Figs., the beam may be found within thisvolume/scan zone. In the embodiment depicted in FIGS. 4 and 5, the conehas a rectangular/square cross-section, as may be seen in FIG. 2. Thusthe scanning area 400 will be rectangular/square shaped. (However, otherembodiments of the present invention may utilize a circularcross-section or an oval shape cross-section. Indeed any shapedcross-section may be utilized as long as the goals of the presentinvention may be obtained.) It is noted that the exact geometry of thisscanning area may not be perfectly square/rectangular in view of thefact that the distance from the receiver 200 to the scanning areachanges with changing angular orientation of the beam with the radiationemitter 200. This phenomenon is discussed in greater detail below.However, for the present discussion, the scanning area will be treatedas a rectangular/square shape that is approximately normal to directionof beam travel away from the radiation emitter 200. It is further notedthat in many embodiments of the present invention, the beam will travelpassed the scanning area 400, if the beam is not intercepted by thereceiver 300. However, some embodiments of the present invention aresuch that the beam does not travel a significant distance beyond thereceiver 300 so that the beam may not be easily detected beyond closeproximity to the refueling aircraft 1000.

In a first embodiment of the invention, the radiation emitter 300 emitsa focused optical beam that is a focused optical elongated beam 210 andscans the beam over the scanning area, as may be seen in FIG. 6. FIG. 7shows the beam from the perspective of the scanning area, which isapproximately normal to the direction of travel of the beam. That is, ifthe scanning area was a flat surface, and the beam 210 impinged upon theflat surface, the beam would look approximately like that shown in FIG.7 when viewed in the direction of beam travel. In a first exemplaryembodiment, the radiation emitter 300 first scans the focused opticalelongated beam 210 over the scanning area starting from the top of thescanning area and ending at the bottom of the scanning area, inincrements, as may be seen, for example, in FIG. 8. (Note that in otherembodiments, the scanning may begin at the bottom and/or at the left orright sides (discussed below) and/or at any other location within thescanning area.) FIG. 8 shows, in a time-elapsed fashion, that at T₁, thebeam 210 is at a first position. At T₂, the beam 210 is moved to asecond position below T₁. At T₃, the beam 210 is moved to a thirdposition below T₂. Again, the beam depicted in FIGS. 6-8 show the resultof the focused optical beam as it would be if the beam impinges on thescanning area 400. FIG. 9 shows the focused optical beam impinging uponthe scanning area over times T₁ through T₁₃ in a time-elapsed manner.

After scanning from the top of the scanning area to the bottom of thescanning area, the radiation emitter changes the orientation of thefocused optical beam 210 from a horizontal orientation to a verticalorientation, as may be seen in FIG. 10. FIG. 11 shows the “impingement”of the beam 210 on the scanning area when the beam is elongated in thevertical direction. As may be seen in FIG. 12, radiation emitter 300scans the beam 210 over the scanning area 400 starting from left toright, in increments. That is, at time T₁₄, the elongated beam impingesupon the scanning area in the left-most position. At T,5, the beam ismoved from the left-most position to a position to the right. At T₁₆,the beam is again moved further to the right. FIG. 13 shows a timeelapsed view of beam impingement over the scanning area from time T₁₄ totime T₂₆.

Thus in comparing FIG. 13 with FIG. 9, it may be seen that the radiationemitter passes the beam over the scanning area in a two-pass or adual-pass manner: first from top to bottom, and then from left to right(or from left to right, and then from top to bottom, etc.)

Positioning Coordinate System

According to a first embodiment of the present invention, at least aportion of the scanning area 400 includes a positioning area 450, as maybe seen in FIGS. 14 and 15, in which the receiver 300 is likely to belocated. In this embodiment of the invention, this positioning area 450is entirely within the scanning area 400, as may be seen in FIG. 15, andthus the optical beam is scanned over the entire positioning area 450.However, in other embodiments, the boundaries of the positioning area450 may exceed the scanning area 400.

The drogue positioning system is adapted virtually divide at least aportion of this positioning area 450 into a virtual grid 460. Thevirtual grid may include a plurality of distributed distinct sectorsthat spatially correspond to sub-areas within the positioning area. Thesub-areas are dispersed within the positioning area in a geometricallydefined manner. As may be seen in FIG. 15, receiver 300 of the refuelingdrogue assembly, during normal operation of the drogue positioningsystem, is typically located within this positioning area, and thus thereceiver 300 will receive radiation from the radiation emitter, duringnormal operational conditions, as the radiation passes over thereceiver. FIG. 16 shows a focused optical elongated beam in thehorizontal position scanning over a row of distinct sectors/sub-areaswithin the virtual grid/positioning area 460/450. In a first embodimentof the present invention, the focused optical elongated beam scans fromtop to bottom in a continuous or in a step-wise manner, such that thefocused optical elongated beam is scanned over each row of distinctsectors/sub-areas. After scanning over all of the rows, the focusedoptical elongated beam is then focused to be elongated in the verticaldirection and is scanned over the positioning area, from column tocolumn, again either in a step-wise or a continuous manner (see FIG.17). As the optical beam moves from row to row and from column tocolumn, the discernable property of the beam changes in a manner thatmay be detected by the receiver 300. That is, were the receiver todetect a discernable property of the horizontal beam while in, forexample, the second row (that is, the discernable property correspondsto horizontal beam positioning within the second row), the radiationreceiver will be able to detect a different discernable property werethe beam and the receiver in the third row and so on. As noted above,the receiver is adapted to output a signal that is indicative of thediscernable property of the received radiation, to convey information tothe signal processor 500.

Drogue (Receiver) Positioning

As noted above, the distributed distinct sectors of the positioning areacorrespond to sub-areas within the positioning area, the sub-areas beingdisbursed within the positioning area in a geometrically defined manner.This geometrically defined manner corresponds to a known orientation ofthe sub-areas with the radiation emitter 200. Therefore, the orientationof the virtual grid 460 with respect to the radiation emitter is known.By way of example and not by limitation, FIG. 18 shows that the centerof the grid 450 is located 100 feet behind and 10 feet below thereceiver 300. (The center of the grid 450 is centered with the radiationemitter 300—i.e. the “X” value is 0.)

Because the orientation of the scanning area/virtual grid with respectto the radiation emitter 300 is known, the discernable property of theoptical beam may be changed to correspond to the particular distinctsectors/sub-areas within the positioning area such that a uniquediscernable property may be carried on the optical beam for eachdistinct sector/sub-area. In this manner, the receiver 300, havingreceived the radiation from the radiation emitter 200 outputs the signalto the signal processor 500 indicative of the distinct property carriedon the optical beam received by the receiver 300, and thus, depending onthe discernable property of the received radiation received by thereceiver 300, by comparing the received discernable property to thosein, for example, a memory, the signal processor 500 can determine whichparticular distinct sector/sub-area the receiver was located in when thereceiver received the radiation.

The following is an exemplary scenario in which the drogue assembly 100determines its position utilizing the first embodiment of the invention.Referring to FIGS. 19 and 20, receiver 300 is located within row 2 andcolumn 11 of the virtual grid 460. Radiation emitter 200 makes a firstpass over the scanning area, and thus the positioning area, with thefocused optical elongated beam, starting from the top of the scanningarea and moving to the bottom of the scanning area, moving the beam fromrow to row. The discernable property of the beam is changed as the beammoves from row to row. When the beam passes over/through row 2, thereceiver 300 detects radiation, and likewise detects the discernableproperty carried on the optical beam, the receiver 300 outputs a signalindicative of the discernable property of the received radiation tosignal processor 500 which determine that the discernable property isindicative of beam location in row 2. The radiation emitter 200continues to scan the beam over the scanning area. Once it reaches thebottom of the scanning area, the radiation emitter 200 then changes theorientation of the beam such that it is elongated in the verticaldirection and scans the scanning area from left to right, moving thebeam through each column in the virtual grid 460, changing thediscernable property carried on the optical beam as the beam moves fromcolumn to column. When the beam passes over column 11, the radiationreceiver receives radiation and outputs a signal indicative of thediscernable property carried on that received radiation. The signalprocessor 500 receives the signal and analyzes the signal to determinethat the discernable property is indicative of beam location in column11. The signal processor 500, remembering that the prior signal wasindicative of a beam position in row 2, recognizes that the receivermust be in column 11 and row 2 of virtual grid. (Note that in mayembodiments of the present invention, the two-pass scan takes placerelatively swiftly with respect to the dimensions of the virtual gridsuch that any movement of the drogue assembly/receiver during that timeis negligible.) Because the virtual grid corresponds to sub-areas of thepositioning area, by recognizing that the signal processor 500 receiveda signal indicative of beam location in the distinct sector of row 2 andthe distinct sector of column 11, and that these sectors correspond toone another, the signal processor 500 may determine the location of thereceiver within the positioning area, and thus determine the position ofthe receiver relative to the radiation emitter, because the position ofthe virtual grid relative to the radiation emitter is known.

FIG. 21 shows implementation of another embodiment of the presentinvention. Instead of utilizing a focus optical elongated beam in atwo-pass/two-scan manner, this embodiment utilizes a traditionalnon-elongated optical beam, as shown, such that when the beam impingeson the scanning area, the beam forms a circle as opposed to an elongatedline. In this embodiment, instead of scanning the beam in a two-passmanner over the scanning area, the radiation emitter 200 scans the beamin an X-Y raster over each of the individual discrete areas of thevirtual grid 450. In this embodiment, the discernable property carriedon the beam changes in a predetermined manner as the beam moves fromeach discrete area such that each discernable property is indicative ofa specific discrete area within the virtual grid corresponding to asub-area within the locating area. By way of example only and not by wayof limitation, in reference to FIG. 21, the radiation emitter 200 scansthe beam 280 across the virtual grid starting at block 1 (discretesector 1), moving the beam from block 1 to block 2, then to block 3,etc., over to block 13, and then moves the beam to block 14, and thenmoves the beam to block 15, block 16, etc., repeating this pattern untilthe beam has scanned over all of the blocks. This scan is thenautomatically repeated. In the scenario depicted in FIG. 21, when thebeam passes over box 24, the receiver 300 will receive the radiation,and thus the discernable property indicative of the beam when directedtowards box 24, and then output a signal indicative of the discernableproperty of received radiation to the signal processor 500. The signalprocessor 500 then determines that the radiation receiver is located inbox 24.

It is noted that in the above description of the X-Y raster, the beamwas moved from box 13 at the upper right side of the grid, all the wayon the left side of the grid. In another embodiment of the presentinvention, a raster scan may include, for example, moving the beam frombox 13 to box 26, after which the beam is moved to box 25, box 24, etc.,all the way to box 14, and then moved to box 27, and then to 28, andthen to 29, etc., all the way to 39, and then moved to box 52, and thento 51, etc. Thus, the raster scan includes both the traditional scanperformed by a cathode ray tube, as well as non traditional rasterscans. Other scanning patterns may be used as well.

It is noted that in the above-described embodiments, the beam scans overthe entire scanning area/virtual grid. Other embodiments of the presentinvention may be implemented where the beam only scans over a portion ofthe scanning area/virtual grid. By way of example only and not by way oflimitation, such may be the case in a system where the signal processor500 is in communication with the radiation emitter 200 such that afterthe processor 500 determines a general area within the grid in which thereceiver 300 is located, the radiation emitter 200 may concentrate thebeam on that general area, as opposed to over the entire area of thescanning area. That is, for example, if the signal processor 500continues to determine that the receiver is in box 24, or is in the areaof box 24, the radiation emitter 200 would not scan the area, say forexample, around box 121. However, if the signal processor 500 did notreceive a signal indicative of radiation within the area of box 24 forwithin a certain time period, the signal processor 500 may direct theradiation emitter 200 to again scan over the entire area so as toincrease the likelihood that the receiver 300 will receive radiation.This may also be done in the case of the focused optical elongated beammethod of scanning as well.

Drogue Assembly Position Control (Station-Keeping)

An embodiment of the present invention, utilizing the drogue positioningsystem detailed above, to control the position of a refueling drogue,will now be described by way of an exemplary scenario. As a preliminarymatter, it is noted that drogue control may be implemented according tothe teachings of U.S. patent application Ser. No. 10/697,564 filed onOct. 31, 2003, entitled Stabilization of a Drogue Body, the contents ofwhich are incorporated herein in their entirety. U.S. patent applicationSer. No. 10/697,564 claims priority to U.S. Provisional Application Ser.No. 60/498,641 filed on Aug. 29, 2003, the contents of which are alsoincorporated by reference herein in their entirety, the teachings ofwhich may also be used to control the position of a refueling drogue.

Initially, the drogue 100 is extended from a drogue carrier attached toa wing of an aircraft 1000. The drogue assembly 100 will be extended asufficient distance from the aircraft 1000 so that aerial refueling maybe conducted. This distance, in an exemplary embodiment, is about 100feet from the wing (and thus the radiation emitter), although in otherembodiments, this distance may differ based on the local conditionsand/or the type of mission required for the aerial refueling. Therefueling drogue assembly 100 will be permitted to obtain a nominalposition/effectively constant position (a constant position the locationof which will vary with different atmospheric conditions, aircraftspeed, etc.) with respect to the aircraft 1000, and thus the radiationemitter 200. At this time, according to this scenario, the aircraft tobe refueled is a sufficient distance away from the refueling drogueassembly 100 such that the aircraft to be refueled does not impart anyforces onto the drogue that may cause the drogue's position to move.

As noted above, wind gusts, turbulence, the receiver aircraft, etc., mayimpart forces on the drogue assembly 100 that will make the drogue movefrom its “effectively constant position.” Based on empirical and/oranalytical analysis, it is known that, for example, under the given setof circumstances for a particular refueling mission, the position of thedrogue/receiver may be maintained within about a 6 inch radius of anominal location, in some embodiments, within about 2-3 inches, and inothers even smaller, such as about 1-2 inches and/or even less than aninch. In some embodiments, the system accounts for turbulence in thefrequency range of 1-3 Hz that can cause a few feet of droguedisplacement. Moreover, in some embodiments of the invention, thestabilization system may account for bow wave (from the receivingaircraft), which induces translation. Specifically, the system mayaccount for bow wave of steady state that can cause about five feet ofdisplacement and/or 2 to three feet of displacement, depending on suchvariables as, for example, the control surface size, control surfacedeflection, control surface actuator force, etc, of the drogue activecontrol system. Some embodiments of the present invention may beimplemented to account for forces that cause the drogue to move as muchas 10 feet in any direction from a “nominal position” relative to theradiation emitter 200. (For other missions, the drogue could move moreor less.) Accordingly, for this particular mission, the area of likelymovement of the drogue, i.e., this “10 feet in any direction,” willdefine the scanning area 400 in a first embodiment. That is, thegeometry of the scanning area 400 will be set to be 20 feet by 20 feet,centered about the nominal position of the drogue, such that thereceiver 300 is very likely to be located within that area during anormal refueling operation. (For other missions, the area may be 10 feetby 10 feet, 10 feet by 20 feet, or more or less, depending on theconditions of the mission. If refueling is being conducted duringrelatively calm atmospheric conditions, the scanning area would likelybe smaller than a scanning area for un-calm conditions.)

It is noted that the location of the scanning area 400 may be adjustedbased on the nominal location of the drogue assembly. That is, forexample, referring to FIG. 1, for a first type of refueling mission, thenominal location of the drogue may be located, on average, 105 feet inthe Z direction, and minus 5 feet in the Y direction, from the radiationemitter 200. In a second type of refueling mission, the drogue mayinstead nominally be 90 feet from the radiation emitter 200 in the Zdirection, and be negative 15 feet in the Y direction from radiationemitter 200.

It is noted that in some embodiments of the invention, the droguepositioning system is configured to adjust the location of the scanningarea to conform to the location of the receiver 300. By way of example,the radiation emitter 200 may move the scanning area over a wide area toinitially find the nominal location of the drogue, and then refine thescanning area about the drogue. It is noted that in other embodiments ofthe invention, the drogue positioning system may instead simply startoff with a very large scanning area such that the beam may be moredispersed, such as in the instance of use of a focused optical elongatedbeam, thus covering a greater area. Upon identification of the nominallocation of the drogue/receiver, the scanning area may be narrowedaccordingly.

In other embodiments of the present invention, the refueling aircraftmay include a device that detects the nominal location of the drogue,and uses this detection to direct the scanning area. In otherembodiments of the invention, an operator on-board the aircraft 1000directs the scanning area at the drogue.

It is also noted that in some embodiments of the present invention, itis not necessary that the scanning area be centered on the nominallocation of the refueling drogue. Such may be the case in conditionssuch that it is expected that the drogue will move from the nominallocation in some directions more than in other directions.

Once the drogue is nominally located, and the scanning area is directedto this location, the positioning system may begin operating to identifythe position of the drogue within the scanning area. Assuming a virtualgrid having 13 columns and 13 rows, as is exemplarily depicted in FIG.14, if the nominal position of the refueling drogue is known, thescanning area/grid will be positioned such that column 7 and row 7 arepositioned at the nominal location of the refueling drogue. As discussedabove, the radiation emitter 200 may scan over the scanning area, andthus over the virtual grid. The signal processor 500 will determinewhere the receiver/drogue assembly is located within the grid based onthe radiation received by the receiver 300 while the radiation emitter200 scans the scanning area. In this exemplary scenario, if the signalprocessor 500 determines that the drogue/receiver 300 is still locatedat virtual row 7, column 7, the active control system of the drogueassembly will not change its position. However, if, for example, thesignal processor 500 determines that the drogue has moved within thevirtual grid to row 6, column 7, the signal processor 500 will output asignal to the active control system to move the drogue downward (i.e.,in the negative Y direction). The active control system may be commandedto move the drogue downward until the receiver again receives radiationfrom the signal processor that the drogue/receiver is again located atits nominal position. If, for example, the radiation is indicative ofreceiver position in row 7, column 7, the signal processor will tell theactive control system to stop directing the drogue downward. However, iffor example the signal processor determines that the drogue is now atrow 8, column 7, this signal processor will output a signal to theactive control system to direct the drogue upwards, (i.e., in thepositive Y direction). Thus, the drogue positioning system may beutilized in an iterative manner to control drogue location. It is notedthat other embodiments of the present invention may operate in differentmanner. That is, for example, if there is a repeating tendency for thedrogue to move from row 7, column 7 to, for example, row 6, column 7,the active control system may adjust a trim on some of the controlsurfaces of the drogue assembly to direct the drogue back to row 7,column 7, such that this tendency is negated. Basically, the droguepositioning system may be used in any manner that will enable theposition of the drogue to be determined such that the position may beadjusted/controlled utilizing an active control system.

It is noted that in some embodiments of the present invention, thedistal portion of the refueling hose will be the portion of the drogueassembly that is actively controlled. This is because in someembodiments, the drogue assembly 100 may include a flexible joint, whichmay be located between the hose 1 10 and the drogue 105, allowing thedrogue 105 to pivot about the centerline of the hose (see, FIG. 3). Insuch embodiments, it is typically the position of the distal end of thehose that is controlled. In other embodiments, typically, where the hoseis rigidly connected to the drogue 105, it is the position of the drogue105 that is controlled. Accordingly, in some embodiments of theinvention, the receiver is rigidly connected either directly to or byway of a rigid interface to the controlled component. If the position ofthe hose is to be controlled, the receiver will typically be rigidlyconnected to the hose, as may be seen, for example, by FIG. 3. It isnoted that some embodiments of the present invention extend to aretrofit kit including an adapter on which a receiver is mounted thatcouples a drogue 105 to a hose 110. Depending on which component is tobe controlled, the adapter is rigidly connected to that component. Insum, by reference to controlling the location of a refueling drogueassembly, it is meant that at least one point on/in the refueling drogueassembly (drogue, distal portion of the hose, adapter, etc.) iscontrolled, recognizing that other parts of the drogue assembly may notbe controlled.

Specific Features of Some Embodiments

Specific features of the drogue positioning system will now bediscussed.

As noted above, the radiation emitter 200 may output a focus opticalbeam. It will be noted that other embodiments of the present inventionmay utilize other types of radiation. Basically, any type of radiationthat may be utilized to determine the drogue location according to thepresent invention may be used. By way of example only and not by way oflimitation, electromagnetic radiation may be utilized. Such anembodiment may utilize technologies associated with VOR and ILS. Asnoted above, the radiation emitter emits radiation that carries adiscernable property that may be received by a receiver and analyzed.This discernable property is used as a reference by the signal processor200 to determine the location of the receiver/drogue within the virtualgrid and the positioning area. This discernable property, in someexemplary embodiments, is created by modulating the beam with digitaldata blocks that represent the current location of the beam in thescanned area/positioning area. An example of a digital data block may beseen in FIG. 22. FIG. 22 shows a schematic drawing of a modulation of aprojected beam. In FIG. 22, a block is exploded. By way of example,only, this block represents a 20-bit data block typical of the otherblocks. In this block, the first 8 bits are header information, whilethe remaining 12 bits represents information regarding the row or columnat which the focused beam is directed. FIG. 22 shows that the block is0.25 inches in length. This corresponds to the width or height of acolumn or row, respectively, at the tracking area. That is, as the beamscans over the area, the beam is modulated such that modulationsufficient to indicate a column or row is completed as the beam moves0.25 inches in the area. For example, the first 0.1 inch of movementcorresponds to header information, while the last 0.15 inches ofmovement corresponds to the row/column information. Thus, in thisembodiment, the modulation is substantially continuous. (Although inother embodiments, the modulation need not be continuous.) Because insome embodiments the processor 500 is configured to recognize a header,the processor may thus determine that the received radiation isindicative of a new row or column once a new header is received.

In some embodiments of the present invention, modulation is obtained bycycling the intensity of the beam, which in some embodiments correspondsto shutting the beam off (or otherwise blocking the beam) and thenturning the beam on (or otherwise directing the beam to the area). Otherembodiments may utilize multiple intensities. Embodiments of the presentinvention may utilize standard digital modulation techniques, such asthose utilized in encryption, if those modulation techniques may becoupled to beam location/direction.

It is also noted that the discernable property of the beam may be uniqueto a given column and row. That is, every column and every row,collectively, may have different discernable properties associated withthat column/row. For example, column 2 will be associated with adiscernable property that is distinct with all the other discernableproperties for all other columns and rows. Such may be accomplished, forexample, by utilizing a “smart header:” a header that includesinformation pertaining to whether the beam is aligned horizontally orvertically, but still allows for the processor to determine that a newblock is being transmitted (discussed more below). However, otherembodiments of the present invention may utilize the same discernableproperties between columns and rows. For example, column 1 may becorrelated to a discernable property that is the same as that for row 1,row 2, or row 3, etc. However, in such a situation, based only on thediscernable property, without more, the system would not know whetherthe discernable property is indicative of a column position or a rowposition. In such instances, for example, the timing between the firstand the second pass of the two-pass scan may be adjusted such that everyfirst receipt of radiation is a scan from top to bottom (e.g., a scanindicating row position), and every second receipt of radiation is ascan from left to right (e.g., a scan indicating column position), or inany other pre-determined pattern. Such may be determined, by way ofexample, by pausing in-between each scan for a certain amount of time.For example, a scan from top to bottom might be separated by apredetermined time period from the following scan from left to right.The scan from left to right may in turn be separated by differentpredetermined time period. The signal processor 500 may be programmed tolook for different time periods between receipt of outputted signalsfrom the receiver and, from a look-up table, recognize the type of scan.Alternatively, the beam may carry two or more discernable properties atthe same time. For example, one property may be indicative of the typeof scan (either top/down or left/right) and the other may be indicativeof the location within the scan area, i.e., what column/row).

By way of additional example, in the case of utilizing a non-elongated(normal beam) such is shown in FIG. 21, one discernable property may beadjusted to indicate the beam's location within a column, while theother discernable property may be adjusted to indicate the beam'slocation within a row such may be used for two-pass scans as well. Insummary, any type of modulation/change in discernable property ofradiation that may be utilized to correlate beam location within thevirtual grid with respect to the radiation emitter may be utilized topractice the present invention.

It is noted that beam receiver overlap may be utilized to practice thepresent invention. That is, by way of example, some embodiments of thepresent invention may utilize a ratio of 6 to 1 for beam/receiveroverlap, although other embodiments may utilize a larger or smallerratio. Overlap may be obtained by utilizing either a big beam/smallreceiver, or a small beam/big receiver. FIG. 23 shows an exemplaryscenario utilizing an embodiment utilizing a big receiver/small beam. InFIG. 23, the rows (and although not shown, the columns) of the virtualgrid are such that multiple rows (and columns) fit within the receiveraperture when virtually overlaid with the receiver aperture. In theembodiment shown in FIG. 23, 7 rows fully fit within the receiveraperture, although again, more or less rows may be utilized in otherembodiments. In an embodiment according to FIG. 23, the discernableproperty may change at least seven times as the beam moves through eachof the rows, and thus the receiver may output seven signals, each ofwhich indicate a specific discernable signal. This will be, of course,the case for the columns of the grid as well, providing that the columnsare dimensioned similar to the rows of the grid. In this regard, columnsize and row size may be directly correlated to the ability to controlthe beam and to vary the discernable property of the beam.

In a first embodiment of the present invention, it is expected that thecolumns and rows of the virtual grid will be 0.25 inches in height/widthwhen the scan area is about 100 feet from the radiation emitter andabout 10 feet below the radiation emitter. Thus, the discernableproperty of the beam may change as the beam moves 0.25 inches in thesweeping direction. Of course, other embodiments of the presentinvention may use a larger or smaller row/column height/width. By way ofexample, some embodiments may utilize heights/widths of 0.1 inches orless and/or 1.0 inchs or more. In many embodiments of the presentinvention, the discernable property of the beam will change as it movesfrom one column to the other. Thus, the discernable property may changeless frequently for grids utilizing rows and columns that are larger.According to some embodiments of the invention, the scan area will be a120 inch×120 inch square, at 100 feet from the radiation receiver, andthe row/column height/width will be 0.25 inches. Thus, the scan areawill be made up of 480×480 columns and rows (scan lines). However, itwill be noted that other embodiments of the present invention may usedifferent sized/shaped scan areas. By way of example only, and not byway of limitation, a circular scan area may be used where the beam isscanned in a helical pattern, starting from the center and movingoutward. In such an embodiment, again, it may be possible to have aninteractive system such that the scan begins at the center, wherereceiver is most likely to be located, and then scans outward, and oncethe radiation receiver receives the radiation, the radiation emitter maybe controlled to reset the scan again, starting at the center and/or atthe approximate location of the drogue. Other embodiments may utilize arectangular section or any other shaped section that will achieve theresults of drogue positioning, according to the present invention.

In the example of FIG. 23, where the height of each row represents 0.25inches, the receiver will receive fully seven different discernableproperties carried on the received radiation, and output seven differentsignals to the radiation receiver, (or alternatively, output a singlesignal carrying a data package which is indicative of the sevenindicative properties received by the received radiation). In otherembodiments, the receiver simply outputs signals indicative of allinformation received, and lets the signal processor 500 determinewhether a full data set has been received. The signal processor 500 willanalyze the signal(s) and determine that radiation has been receivedthat is indicative of seven different rows within the grid, and thus theexact position within the virtual grid may not necessarily be known. Insome embodiments, the receiver and/or signal processor determine whethera full data set has been received base on the number of bits receivedbetween receipt of headers. For example, in the scenario depicted inFIG. 23, the receiver will not receive a header until row 2, and thuswill know to ignore the information preceding. Also, after receiving theheader of row 9, the receiver will not receive another header, and alsowill not receive a full 20 bits of information before the radiationstops, and thus will know to ignore any information following the lastreceipt of 20 bits. In such a scenario, the receiver and/or signalprocess such that the seven different rows are averaged in a manner suchthat the average row location would be determined. For example, in thefigure of FIG. 23, the average row will be row 5. If, for example, thereceiver aperture was moved downward 1 row such that the average row wasrow 6, the signal processor could output a signal to the activecontroller to adjust the control to move the drogue upward, such thatthe average of the received rows would again be row 5. Still further,referring to FIG. 23, it may be seen that radiation from row 1 andradiation from row 9 would also be received by the receiver, if only ina fractional amount. According to an embodiment of the invention, thispartial received radiation may correspond to only a receipt of a partialdata set, and the receiver may be of a design such that the receiverwill not output a signal upon receipt of only a partial data set/partialamount of radiation. That is, with reference to FIG. 23, the receiverwould only out put seven signals, not nine signals (i.e., the receiverwould basically ignore the radiation of column 1 and column 9. However,other embodiments of the present invention may output a signal upon evenreceipt of a partial data set.

In another embodiment of the invention, the number of bits receivedduring a pass is used to obtain a hyper accurate position within asector/sub-area. Referring to FIG. 23, the processor 500 know the numberof bits that it received, and know that it received a full data set forlines 2 through lines 8. For example, the processor 500 will know thatit received 7×20 bits for rows 2 through 8, that it received, forexample, 5 bits before it received a full 20 bits representing row 2,and that it received 10 bits after it received a full 20 bitsrepresenting row 8. The processor can thus determine that the center ofthe receiver is located closer to row 9 than row 1. In fact, theprocessor can determine that the center of the receiver is about 12.5bits away from the top of row 5 (e.g., 155 bits received, divided by 2,minus the 5 bits received from line 1=72.5 bits below the top of line 2,and if each line represents 20 bits, the center will be 12.5 bits awayfrom the top of row 5—the distance from the bottom of row 5 may bedetermined as well, both to verify the correctness of the calculation,or to smooth possible rounding errors.) Thus, instead of simply beingable to determine that the receiver is centered within row 5, adetermination may be made that the receiver is centered 0.15625 inchesbelow the top of row 5 (12.5 bits divided by 20 bits times 0.25 inches).Other algebraic manipulations may be utilized as well to practice thisembodiment of the invention to obtain hyper accurate results.

A processing algorithm that may be used in the present invention is asfollows. Assuming that the raster is numbered top down and that themessage packets are numbered left to right, the center raster scan lineis:

-   -   A.        Lowest_number_scan_line_detected+((Highest_number_scan_line_detected−Lowest_number_scan_line_detected)/2).    -   B. The center packet is: For the scan line from “A,” above,        lowest_packet        number+((highest_packet_number−lowest_packet_number)/2).

As noted above, embodiments of the present invention may either utilizebig beam/small receiver or a small beam/big receiver. Any size beam andany size receiver may be utilized providing that drogue positioning maybe obtained according to the present invention.

Many of the embodiments, according to the present invention utilize thevirtual grid as detailed above. However, other embodiments of thepresent invention may be practiced without utilizing a virtual grid. Byway of example, a focused optical non-elongated beam, such as thataccording to FIG. 21, may be scanned such that the beam containsdiscernable properties that are indicative of the angular orientation ofthe beam with respect to the radiation emitter. In such a situation, tworeference planes may be created, which may be, but do not necessarilyhave to be orthogonal to one another. For example, FIGS. 24 and 25 showangular orientation from planes extending out of the view passingthrough the nominal angle of beam direction as may be seen. According toFIG. 24, the receiver is located at plus 10 degrees above the planepassing through the nominal angle. According to FIG. 25, the receiver islocated at plus 5 degrees to the side of the plane passing through thenominal angle. If the nominal “location” of the beam is plus 10 degreesand 0 degrees, the active control system may be directed to steer thedrogue back 5 degrees. In such an embodiment, both the elongated beamand the non-elongated beam method of scanning may be used. If thenon-elongated beam method is used, the beam zone, the beam zone mayinclude a plurality of distributed distinct vector of known orientationwith the radiation emitter such that if the signal processor determineswhich distinct vector a received beam coincides with, the orientation ofthe receiver relative to the radiation emitter may thus be determined.That is, the distinct vectors correspond to actual orientations of thebeam with respect to the radiation emitter, the actual orientationsbeing disbursed within the beam zone in a geometrically defined manner.

In such an embodiment, the radiation emitter is adapted to direct a beamof emitted radiation to an area away from the radiation emitter, theradiation including discernable properties that vary in a correspondingmanner with varying orientation of the beam of radiation with respect tothe radiation emitter. By way of example, the radiation emitter isadapted to emit a focused optical beam modulated with digital datablocks, the modulated digital data blocks respectively indicative ofdiscrete orientations respectively corresponding to orientations of thebeam relative to the radiation emitter. Some of the varied discernableproperties are respectively indicative of discrete orientationsrespectively corresponding to orientations of the beam relative to theradiation emitter in a first reference frame, and wherein at least someof the varied discernable properties are respectively indicative ofdiscrete orientations respectively corresponding to orientations of thebeam relative to the radiation emitter in a second reference frame.

Based on the output of the receiver, the processor is adapted to processthe outputted signal and identify a first virtual orientation indicativeof an orientation of the receiver relative to the radiation emitter whenat least a portion of the radiation was received by the receiver. By wayof example, the signal processor is adapted to analyze a first outputtedsignal from the receiver that is indicative of a first discernableproperty of the received radiation indicative of a first discreteorientation corresponding to a first orientation of the beam relative tothe radiation emitter in the first reference frame at the time that theradiation was received. Still further by way of example, the signalprocessor is adapted to analyze a second outputted signal from thereceiver, the second outputted signal being indicative of a seconddiscernable property of the received radiation indicative of a seconddiscrete orientation corresponding to a second orientation of the beamrelative to the radiation emitter in the second reference frame at thetime that the radiation was received. Accordingly, the signal processoris adapted to identify a virtual location of the receiver relative tothe radiation emitter based on the analysis of the first and secondoutputted signals.

As discussed above, some embodiments of the present invention areconfigured to permit the drogue assembly 100 to maintain a positionrelative to the radiation emitter. Such maintenance may be performed insome embodiments without the need for communication between theradiation emitter and the drogue assembly 100. For example, the signalprocessor 500 on the drogue assembly 100 may be furnished with look-uptables sufficient to analyze the signals from the receiver and identifythe current location of the refueling drogue within the positioningarea/virtual grid. However, in other embodiments, the drogue may be incommunication with the refueling aircraft.

An embodiment of the prevent invention include kits that comprisedevices that will enable conventional refueling drogue to be retrofittedfor positioning determination and/or to be actively controlled. (Suchembodiments also extend to methods of conversion as well.) Such devicesmight come in the form of a pack that includes a receiver, a signalprocessor, and/or control surfaces, sensors, etc., necessary toimplement positioning determination and/or active control. In someembodiments of the present invention, a pack may have the positioningsystem and the active control system in one pack, or at least thecomponents that physically interface with the air stream (e.g., thevanes, the control surfaces, etc.) required to implement those systems(the other components may be added directly to the refueling aircraft aslong as there is a means to interface with the retrofit packs). Thus,any kit/pack that contains any or all of the above elements of thedrogue positioning system and/or the active control system and/or willpermit the implementation of the functions of position determinationand/or active control on an existing refueling drogue, may be utilizedto practice some embodiments of the invention

It is further noted that the present invention includes software,firmware and/or computers (including simple logic and/or error circuits)adapted to implement the above techniques. Also, while some embodimentsof the present invention may be practiced manually, other embodimentsmay be practiced automatically. Thus, the present invention includes anydevice or system that may be configured or otherwise used to implementthe present invention in an automated manner.

Some embodiments of the present invention may be configured to generateelectricity at the refueling drogue 100, to power the receiver, thesignal processor and/or the active control system, etc.

As discussed above, the scanning area is treated as being an area thatis flat. However, under such treatment, the distance of the scanningarea to the radiation emitter will be larger at the edges of thescanning area than at the center of the scanning area (assuming ascanning area centered about the nominal direction of the emitted beam),owing to the change in angle of the beam between the center and theedges of the area. Thus, the distinct sectors of the virtualgrid/sub-areas may differ in size between those at the center of thegrid/locating area and those at the edges to account for thisphenomenon. Indeed, in some embodiments of the invention, the grids aredefined by the optical beam. That is, how the beam changes controls thesize and shape of the virtual grid/the sub areas. In this respect, thegrid is more of a convenient way to express location of the drogue. Ifthe present invention is practiced to maintain a position of the drogue,uniformity of the virtual grid is not needed. In fact, the grid could bedispensed with entirely, providing that logic is utilized to control theposition of the drogue. (For example, large look-up tables may beutilized and/or modified fly-by-wire logic may be used corresponding tothe various discernable properties as they correspond to orientation ofthe beam with the radiation emitter. For example, exhaustive if-thenroutines might be utilized.) Alternatively, the angular change of theorientation of the emitted beam may be varied to utilize a consistentlysized grid (i.e., larger angular changes while scanning at the edges ofthe grid/tracking area than while scanning near the center of the grid.Also, a combination of the two may be utilized.

In this regard, the tracking area/virtual grid may be treated as acurved surface instead of a flat area. In this regard, it is noted thatwhen the refueling drogue assembly 100 moves relative to the radiationemitter, it is likely that the assembly 100 will move in threedimensions. That is, assuming that the refueling hose 110 is of aconstant length during refueling, a change in position in the “X” or “Y”direction (referring to FIGS. 1 and 2) will result in a change inposition in the “Z” direction. Thus, embodiments of the presentinvention may be implemented that account for the position of the droguein three dimensions (i.e., a positioning volume may be utilized todetermine the position of the drogue). Such may be accomplished byadding, for example, a second radiation emitter or a second radiationreceiver a know distance from the first radiation emitter or the firstradiation receiver, respectively, and triangulating between the two.Alternatively or in addition to this, some embodiments of the presentinvention might utilize two or more receivers spaced about the drogueassembly that analyze which beam was received by which receiver during agiven pass. For example, if at a distance of 100 feet from the radiationemitter, for a given location within the receiving area, receiver A isexpected to receive radiation carrying a property indicative of receiverposition at column 45 and receiver B is expected to receive radiationcarrying a property indicative of receiver position at column 57, and ifat a distance of 102 feet from the radiation emitter, again for the“same” location within the receiving area receiver A is expected toreceive radiation carrying a property indicative of receiver position atcolumn 44 and receiver B is expected to receive radiation carrying aproperty indicative of receiver position at column 58, the distance inthe “Z” location may be obtained based on this phenomenon, asapplicable.

According to the above, embodiments of the present invention may beimplemented utilizing positioning areas and/or positioning volumes in amanner that will permit drogue positioning/station keeping to beimplemented according to the present invention. In summary, anycoordinate system may be utilized to practice the present invention.

Scaled Test Model

U.S. Provisional Patent Application Ser. No. 60/656,084, entitledOptical Tracking System for Refueling, filed on Feb. 25, 2005, thecontents of which are incorporated herein by reference in its entirety,discloses, among other things, embodiments of the present inventionconfigured for wind-tunnel scaled testing of at least some of themethods, devices, and systems as described herein. It is noted that thepresent invention thus includes the devices, systems and methodsdisclosed therein, scaled or unscaled. The present invention thusfurther includes the devices, systems and methods disclosed thereinscaled for implementation with the teachings herein.

According to some embodiments of the scaled test model, the optical linkis be visible and eye safe; the distance to the target may be about 10feet, the active area of the scan beam (scanning area) may be about 12.8inches by about 12.8 inches at the receiver; the grid resolution at thetarget may be about 0.025″; the beam spot size at the target may beabout 0.015″ diameter or less; the frame rate may be about 100 Hz; thereceiver active area may be about 0.250″ diameter or more; and thereceiver may have a field of view of 300 (i.e. a conic included angle of300). Still further, according to some embodiments of the scaled testmodel, there may be 512×512 scan lines in a frame; there may be 18 bitsminimum of encoding information on the beam for each position on thetarget grid such that (assuming 18 bits) a 26.2144 MHz data rate will beachieved, i.e., 512×512×100=26.2144 MHz data rate; encoding on the beammay be of a form that permits quick recognition that only a partial dataframe has been received; sync and/or framing bits may be permitted,while recognizing that the data rate increases proportionally with theadditional bits; and a single complete block of position data may take0.78 μs. Such features may be scaled for implementation in a system asdescribed herein for aerial refueling. By way of example, in someembodiments, it is expected that a frame (e.g., an complete horizontaland vertical scan) may be completed with a speed such that 20frames/second may be accomplished. That is, one frame may beaccomplished in 50 milliseconds. By way of example, a horizontal scanmight take 20 milliseconds, and a vertical scan might take 20milliseconds.. If there were 500 rows/columns per scan, at 20 bits perrow/column, 10,000 bits of information would be conveyed in 20milliseconds.

The output of the receiver function may be an RS-232 data streamcontaining 3 bytes of data and running at 115.2 Kilo Baud. This data maybe only the 18 bit position information without any sync or header bits.This message may be the code for the frame that is nearest the center ofthe receiver. This may be determined by analyzing all complete frameswithin the field of view of the receiver. This message stream may repeatat 100 Hz. Synchronization of the 3 byte frame may be either relative tothe start of a complete scan frame or relative to the receiverprocessing element.

The transmitter may be self contained and may require only power appliedto function. All beam forming, scanning, and modulation elements may besupplied. The transmitter may optionally be in two parts: an opticalhead; and an electronics assembly. Separation of up to 8 inches may bepresent between the optical head and the electronics if the transmitteris a two part unit.

The mounting on the receiver may have dynamic motion up to a frequencyof 10 Hz; this motion may include both translation and rotation.Assuming an edge to edge motion over the 12.8 inch range at 10 Hz, thereceiver will move 10 inches per 0.1 s. (i.e., at a rate of 100 inchesper 1.0 s=0.0001 inches per 1.0 μs).

Although ambient light directed into the receiver may not be eliminated,it can be reduced or be made to be indirect. Moreover, although thereceiver may be bandwidth limited by the use of optical filters, theoperating wavelength may be in the visible band and, therefore, ambientlight may still be present.

An exemplary implementation of an embodiment of the invention suitablefor wind tunnel testing is as follows, and may be scaled accordingly foractual implementation.

A two-axis design may be utilized. Multiple optical paths, multiple scanconfigurations for a given optical path may be used. UV lasers or redlasers may be used. Single or dual galvanometer designs may be used. Aninternal line generator or an external line generator may be used. Infact, an “internal-external line generator” may be used, because withoutan internal line generator, the laser beam may be wide enough to appearon both the X and Y turning mirrors simultaneously, and thus appeared inthe X and Y scan fields simultaneously. An internal line generator isthus useful, but the device may also have external line generatingoptics. Indeed, in some embodiments, a single galvo or dual galvo,either having internal LG optics, external LG optics or internal andexternal LG optics, may be utilized. A single galvo with internal linegenerator may be used, having three simple mirrors. Two sizes may beused: ½″×½″ and 1″×1″. Small line generation optics are used, with asimple optics mounting. FIGS. 26 to 31 schematically represent variousgalvo designs, while FIGS. 32 to 33 b schematically represent beamemission in elapsed time. It should be noted that the axisrepresentations in these figures may not correspond exactly to those inthe prior figures. In an exemplary embodiment, the radiation emitterincludes a single line optical beam emitter, a prism, and a rotatablemirror assembly, wherein the radiation emitter is adapted to rotate therotatable mirror assembly so that a single line optical beam emitted bythe single line optical beam emitter is deflected by the mirror toproject the emitted single line optical beam in a first orientation. Theradiation emitter is further adapted to rotate the rotatable mirrorassembly so that the single line optical beam emitted by the single lineoptical beam emitter passes through the prism to project the emittedsingle line optical beam in a second orientation different from thefirst orientation. In this manner, a single optical beam projector(e.g., laser) may be used instead of two projectors (laser generators).Of course, other embodiments of the present invention may utilizemultiple generators that are synchronized to obtain lines at variousorientations.

Regarding line quality and characteristics, to obtain a beam width of0.25″ at 75 feet, using a UV laser diode with an emitting region ofapproximately one micron in width, a diffraction-limited cylindricallens of at least 3 mm diameter is used, located at least 3 mm from theemitting region. Accordingly, a line width of 2 mm at a range of 8 feet,using a 635 nm laser, and a line width of 10 mm at 75 feet, with thesame laser module may be obtained.

Since scanning may be done by a single axis scanner, rather than atip-tilting plate, scans in the X and Y directions may have differentvirtual centers. The apparent sources of the X and Y scans are separatedby approximately 9 mm in the X-direction, 13mm in the Y-direction, and13.5 mm in the Z direction (again, these axis may not correspond tothose in the figures previously referred to herein). This has twoeffects on the scan registration at the sensor, both of which are minorat more than several feet working distance. The first effect is due tothe apparent lateral separation of the sources. This parallax errorresults in the misregistration of the X- and Y-scans with changingranges. The effect is about the same as what one would see if one held aflashlight in each extended hand, and aimed them at a single object.Objects both closer and farther away would register in different partsof the two beams. The effect is very small, though, since the virtualseparation of the sources in the actual device is only about 16 mm. Whenthe object is 8 feet away, the beam centers diverge at arctan(1 6/2400),or 0.38 degrees. This would result in a mis-registration of 1 mm forevery 6 inches change in range. At a range of 75 feet, it would resultin a mis-registration of 1 mm for every 56 inches change in range.Moreover, computers may be used to compensate for this. The onlypractical effect of this mis-registration is to reduce the coincidentarea over which both beams scan, as the range changes. Because the beamsgrow with range, the parallax error shrinks as a percentage of the areascanned. When the beams are aligned at 75 feet, this parallax error willcause the beams to overlap by only 90% when the range shrinks to 10 feetor so, 100% at 75 feet, and about 95% at one mile. For testing thesystem will be aligned at a range of 8 feet.

The second effect is due to the apparent longitudinal separation of theX and Y beam sources. This effect causes the Y beam to scan an areawhich is 1.3 mm larger than the X beam at any given range. This effectis negligible at all ranges where the beams are coincident.

The mirrors in the scanner are oriented to minimize errors of the scan.These errors take the form of coincidence errors, perpendicularityerrors and keystone errors. Keystone errors cause the scan to travelfarther along one edge than the other (the beam is actually sweeping outpart of a large circle in the image plane), resulting in a keystoneshaped scanned area. Perpendicularity errors cause the X and Y scans totravel at an angle other than 90 degrees to each other. Coincidenceerrors cause the centers of the X and Y scans to be non-coincident inthe image plane. The result of these errors is to reduce the area ofcoincidence over which the X and Y scans travel and, in the case ofperpendicularity errors, add crosstalk between the two axis. The mirrorsare arranged so that all of these errors are normally either zerothroughout the scan or at a minimum (zero) at the center of the scan.

Manufacturing errors in the mirror supports can move the orientations ofthe mirrors away from their designed positions, and thus cause theabove-mentioned errors to become non-zero. Typical manufacturing errorsare on the order of 0.003″. Assuming that each of the mirrors has a tilterror of this magnitude across its surface, the resulting scanned areaat a range of 75 feet would be significantly reduced.

Manufacturing errors can be corrected by building into the device an Xtilt adjustment on the X scan mirror and a Y tilt adjustment on the Yscan mirror. When those two adjustments are used to correct themanufacturing errors, the resulting scan can be restored to nearly itsoriginal condition. Even if some error, such as perpendicularity error,remains, as long as it is small, it may be effectively ignored.

The following material might be used to implement this embodiment: Afabricated XY scan mirror support block, a fabricated X scan mirrorsupport block a fabricated Base, a fabricated Y scan mirror supportblock, a fabricated Laser support block, a fabricated Scanner supportblock a fabricated Laser aperture, a Thorlabs 2nd Y-scanmirror-ME1S-G01, a Thorlabs 1st Y-scan mirror—ME1S-G01, a Thorlabs Xscan mirror—ME05S-G01, a Nuffield Technology, Inc. Scanner Mirror—10 mmX mirror, assembly, a Nuffield Technology, Inc. Scanner—Part No. HS-15C,a World Star Tech Laser Module—Part No. UTL5-10G-635.

FIGS. 34-39 present an example of a design for a scanner head, which isapproximately 4×4×4 inches in dimension.

In some embodiments, the scan area is 2′×2′ at 12′ distance. Operationis at 25 Hz. FIGS. 34-39 schematically represent an emitter according toan embodiment of the present invention.

Again, the above may be scaled for actual implementation.

It is noted that while the above has been described in terms ofapplication for determining a position of a refueling drogue relative toa reference point, and thus controlling the position of the refuelingdrogue relative to a refueling point, other embodiments of the presentinvention might be utilized to determine the location of other types oftargets and/or control the location of those targets. Such targets mayinclude, for example, aircraft, landcraft, boats, autonomous drones,satellites, etc. Indeed, some embodiments of the present invention maybe implemented by placing a radiation emitter up on a tower, andscanning an area below the tower, such as a runway, a parking lot, aconstruction site, etc, and using the invention to control/positionautonomous drones, autonomous vehicles (alleviating the need for aparking attendant), construction equipment such as bulldozers, etc.

Given the disclosure of the present invention, one versed in the artwould appreciate that there may be other embodiments and modificationswithin the scope and spirit of the present invention. Accordingly, allmodifications attainable by one versed in the art from the presentdisclosure within the scope and spirit of the present invention are tobe included as further embodiments of the present invention. The scopeof the present invention accordingly is to be defined as set forth inthe appended claims.

1. An aerial refueling system comprising: a refueling drogue assemblyincluding a refueling drogue and a refueling hose in captive relationwith the refueling drogue; and a drogue positioning system, the droguepositioning system including a radiation emitter, a radiation receiverand a signal processor; wherein the radiation emitter is adapted todirect radiation to a positioning area a defined distance from theradiation emitter, the radiation carrying a modulated location signalcontaining information corresponding to positions within the positioningarea; wherein the radiation receiver is adapted to receive at least aportion of the emitted radiation carrying the modulated signal andoutput a signal to the signal processor indicative of the modulation ofthe location signal of the received radiation; and wherein the signalprocessor is adapted to process the outputted signal and identify aposition within the positioning area indicative of the location in thepositioning area of the received radiation.
 2. The system of claim 1,wherein the radiation emitter is adapted to emit a focused optical beamand scan the focused optical beam over the positioning area.
 3. Thesystem of claim 1, wherein the emitted radiation is a focused opticalbeam, wherein the modulated location signal includes a plurality ofdigital data blocks, the plurality of digital data blocks containinginformation respectively corresponding to a plurality of discretepositions within the positioning area that respectively correspond to acurrent location of the focused beam within the positioning area.
 4. Thesystem of claim 3, wherein the radiation emitter is adapted to emit afocused optical beam and scan the focused optical beam over thepositioning area.
 5. The system of claim 2, wherein the radiationemitter is adapted to emit a focused optical beam and scan the focusedoptical beam over the positioning area in an X-Y raster.
 6. The systemof claim 2, wherein the radiation emitter is adapted to emit a focusedoptical elongated beam and scan the focused optical elongated beam overthe positioning area in a dual-pass manner.
 7. The system of claim 2,wherein the radiation emitter is adapted to emit a focused optical beamand scan the focused optical beam over the positioning area in a spiralpattern, the spiral pattern having a focus at the approximate center ofthe positioning area.
 8. The system of claim 3, wherein the radiationreceiver is adapted to receive at least a portion of the focused beamwhen at least that portion of the focused beam is directed at theradiation receiver, and wherein the signal outputted by the receiver isindicative of the information contained in at least one digital datablock carried by the received radiation.
 9. The system of claim 3,wherein the radiation receiver is adapted to receive at least a portionof the focused beam when at least that portion of focused beam isdirected at the radiation receiver and determine whether a full digitaldata block carried by the focused beam has been received, and only if afull digital data block has been received, output the signal to thesignal processor, wherein the outputted signal is indicative of theinformation contained in the full digital data block received.
 10. Thesystem of claim 1, wherein the radiation emitted by the radiationemitter is a focused beam and the radiation emitter is adapted to scanthe focused beam over the positioning area; wherein the droguepositioning system is adapted to virtually divide at least a portion ofthe positioning area into a virtual grid, the virtual grid including aplurality of distributed distinct sectors, the distributed distinctsectors spatially corresponding to sub-areas within the positioningarea, the sub-areas being disbursed within the positioning area in ageometrically defined manner; wherein the drogue positioning system isadapted to change the modulated location signal carried on the focusedbeam as the focused beam is scanned over the positioning area, whereinchange in the modulated location signal corresponds in a defined mannerto the sub-areas such that a modulated location signal indicative of abeam being directed at a first sub-area is distinct from a modulatedlocation signal indicative of a beam being directed at a secondsub-area; and wherein the signal processor is adapted to analyze one ormore outputted signals from the receiver indicative of the modulation ofthe location signal and identify a distinct sector corresponding to thereceived modulated location signal carried on the focused beam.
 11. Thesystem of claim 10, wherein the signal processor identifies a sub-areaat which the beam is directed based on the identification of thedistinct sector corresponding to the received modulated location signalcarried on the emitted radiation.
 12. The system of claim 10, whereinthe signal processor is adapted to analyze a first outputted signal anda second outputted signal outputted after the first outputted signal todetermine a location in the virtual grid at which the distinct sectorscoincide; the first and second outputted signals being respectivelyindicative of the modulation of the location signal of the beam receivedby the receiver.
 13. The system of claim 12, wherein the signalprocessor identifies a sub-area at which the beam is directed based onthe determination of the location in the virtual grid at which thedistinct sectors coincide.
 14. The system of claim 12, wherein theradiation emitted by the radiation emitter is a focused opticalelongated beam and the radiation emitter is adapted to scan the focusedoptical elongated beam over the positioning area in a dual-pass manner,wherein the first outputted signal is generated by the reception of atleast a portion of the focused optical elongated beam in a first pass ofthe beam over the positioning area, and wherein the second outputtedsignal is generated by the reception of at least a portion of thefocused optical elongated beam in a second pass of the beam over thepositioning area.
 15. The system of claim 14, wherein the focusedoptical elongated beam of the first pass is normal to the focusedoptical elongated beam of the second pass.
 16. The system of claim 14,wherein the drogue positioning system is adapted to identify thelocation of the receiver within the positioning area based on thecoincidence of the first optical elongated beam and the second opticalelongated beam.
 17. The system of claim 1, wherein the aerial refuelingsystem includes an active control system adapted to regulate theposition of the refueling drogue assembly with respect to a refuelingaircraft when the refueling drogue is extended from the refuelingaircraft.
 18. The system of claim 11, wherein the radiation receiver ismounted on the refueling drogue assembly, wherein the aerial refuelingsystem includes an active control system adapted to regulate theposition of the radiation receiver within the positioning area when therefueling drogue is extended from a refueling aircraft.
 19. The systemof claim 18, wherein the active control system is adapted to regulatethe vertical and horizontal position of the drogue to maintain asubstantially fixed orientation of the receiver within the positioningarea.
 20. The system of claim 17, wherein the active control system isadapted to regulate a position of the radiation receiver so that theposition of the radiation receiver is substantially constant within thepositioning area.
 21. An aerial refueling system comprising: a refuelingdrogue assembly including a refueling drogue and a refueling hose incaptive relation with the refueling drogue; and a drogue positioningsystem, the drogue positioning system including a radiation emitter, aradiation receiver, and a signal processor; wherein the radiationemitter is adapted to direct a beam of emitted radiation to an area awayfrom the radiation emitter, the radiation including discernableproperties that vary in a corresponding manner with varying orientationof the beam of radiation with respect to the radiation emitter; whereinthe radiation receiver is adapted to receive at least a portion of theemitted radiation and output a signal to the signal processor indicativeof one or more of the discernable properties of the received radiation;and wherein the processor is adapted to process the outputted signal andidentify a first virtual orientation indicative of an orientation of thereceiver relative to the radiation emitter when at least a portion ofthe radiation was received by the receiver.
 22. The system of claim 21,wherein the radiation emitter is adapted to emit a focused optical beammodulated with digital data blocks, the modulated digital data blocksrespectively indicative of discrete orientations respectivelycorresponding to orientations of the beam relative to the radiationemitter. 23 The system of claim 22, wherein at least some of the varieddiscernable properties are respectively indicative of discreteorientations respectively corresponding to orientations of the beamrelative to the radiation emitter in a first reference frame, andwherein at least some of the varied discernable properties arerespectively indicative of discrete orientations respectivelycorresponding to orientations of the beam relative to the radiationemitter in a second reference frame.
 24. The system of claim 23, whereinthe signal processor is adapted to analyze a first outputted signal fromthe receiver, the first outputted signal being indicative of a firstdiscernable property of the received radiation indicative of a firstdiscrete orientation corresponding to a first orientation of the beamrelative to the radiation emitter in the first reference frame at thetime that the radiation was received, and wherein the signal processoris adapted to analyze a second outputted signal from the receiver, thesecond outputted signal being indicative of a second discernableproperty of the received radiation indicative of a second discreteorientation corresponding to a second orientation of the beam relativeto the radiation emitter in the second reference frame at the time thatthe radiation was received; and wherein the signal processor is adaptedto identify a virtual location of the receiver relative to the radiationemitter based on the analysis of the first and second outputted signals.25. The system of claim 22, wherein the radiation receiver is adapted toreceive the focused beam carrying the digital data blocks when thefocused beam is directed at the radiation receiver and output the signalto the signal processor, wherein the outputted signal is indicative ofthe information contained in a digital data block carried on thereceived beam, and wherein the processor is adapted to analyze theoutputted signal from the receiver indicative of the informationcontained in the received digital data block and identify theorientation of the beam relative to the radiation emitter based on theinformation contained in the received digital data block to identify thefirst virtual orientation.
 26. The system of claim 21, wherein theradiation emitted by the radiation emitter is a focused beam and theradiation emitter is adapted to scan the focused beam over the area;wherein the drogue positioning system is adapted to virtually divide atleast a portion of the various possible orientations of the beamrelative to the radiation emitter into a beam zone, the beam zoneincluding a plurality of distributed distinct vectors, the distributedvectors spatially corresponding to actual orientations of the beam withrespect to the radiation emitter, the actual orientations beingdisbursed within the beam zone in a geometrically defined manner;wherein the radiation emitter is adapted to change the modulated signalcarried on the focused beam as the focused beam is scanned over the areato obtain different modulated signals, the different modulated signalscorresponding in a defined manner to the actual orientations such that amodulated signal indicative of a beam being directed along a firstorientation is distinct from a modulated signal indicative of a beambeing directed along a second orientation; and wherein the signalprocessor is adapted to analyze the outputted signal from the receiverindicative of the modulation of the signal and identify the distinctvector corresponding to the received modulated signal carried on theemitted radiation.
 27. The system of claim 26, wherein the signalprocessor is adapted to identify the orientation of the receiverrelative to the radiation emitter based on the identified distinctvector.
 28. The system of claim 26, wherein the signal processordetermines at least one of (i) the distinct vector along which the beamis directed based on the identification of the distinct vectorcorresponding to the received modulated signal carried on the emittedradiation and (ii) the orientation along which the beam is directedbased on the identification of the distinct vector corresponding to thereceived modulated signal carried on the emitted radiation.
 29. Thesystem of claim 21, wherein the aerial refueling system includes anactive control system adapted to regulate the position of the refuelingdrogue with respect to a refueling aircraft when the refueling drogue isextended from the refueling aircraft.
 30. The system of claim 29,wherein the radiation receiver is mounted on the refueling drogueassembly, wherein the aerial refueling system includes an active controlsystem adapted to regulate the position of the radiation receiver whenthe refueling drogue is extended from a refueling aircraft.
 31. Thesystem of claim 29, wherein the active control system is adapted toregulate the vertical and horizontal position of the drogue to maintaina substantially fixed orientation of the receiver with respect to theradiation emitter.
 32. A method of positioning a refueling drogue,comprising: extending a refueling drogue assembly including a refuelingdrogue and a refueling hose in captive relation with the refuelingdrogue from a refueling aircraft; scanning a focused optical elongatedbeam from a radiation emitter onboard the refueling aircraft over apositioning area a defined distance from the radiation emitter;modulating a signal carried on the beam as the beam is scanned over thepositioning area in a manner corresponding to positions of the beamwithin the positioning area; receiving the optical beam carrying themodulated signal with a receiver on the refueling assembly; andanalyzing the modulation of the signal carried on the received opticalbeam to determine a position within the positioning area of the receiverat the time the radiation was received.
 33. The method of claim 32,further comprising scanning the focused optical elongated beam over thepositioning area in a two-pass manner and receiving the focusedelongated beam scanned in a two-pass manner.
 34. The method of claim 33,further comprising receiving the optical beam scanned in a first pass ofthe two-pass scan and receiving the optical beam scanned in a secondpass of the two-pass scan and comparing the beams received in the firstpass and the second pass and determining the position of the receiverwithin the positioning area based on a correspondence of position of thebeams within the positioning area of the beams.
 35. The method of claim33, further comprising receiving the optical beam scanned in a firstpass of the two-pass scan and receiving the optical beam scanned in asecond pass of the two-pass scan and comparing the beams received in thefirst pass and the second pass and determining the position of thereceiver within the positioning area based on a correspondence ofposition of the received beams within the positioning area.
 36. Themethod of claim 32, further comprising actively controlling therefueling drogue assembly to maintain a substantially fixed positionrelative to the radiation emitter based on the determined positionwithin the positioning area of the receiver.
 37. The system of claim 1,wherein the radiation emitter includes: a single line optical beamemitter; a prism; and a rotatable mirror assembly; wherein the radiationemitter is adapted to rotate the rotatable mirror assembly so that asingle line optical beam emitted by the single line optical beam emitteris deflected by the mirror to project the emitted single line opticalbeam in a first orientation; and wherein the radiation emitter isadapted to rotate the rotatable mirror assembly so that the single lineoptical beam emitted by the single line optical beam emitter passesthrough the prism to project the emitted single line optical beam in asecond orientation different from the first orientation.